Cutter head



May 14, 1929.

C- WOLF CUTTER 111mb Filed Sept. 1'7, 1927 wl i J rz'wrzfors Jfg/as WPatented May 14, 1929,

UNITED STATES CHARLES WOLF, OF WORCESTER, MASSACHUSETTS.

CUTTER HEAD.

Application filed September My invention relates to cutter heads of thetype ordinarily employed for cutting and planting wood, such devicesbeing charact-erisced by the employment of a rotary block or headcarrying a number of radially disposed cutting tools or knivespresenting cutting edges extending parallel to the axis of rotation ofthe head.

It is desirable to operate cutting heads of the above described type ata high speed of rotation which makes it essential that the tools orknives be firmly held so that the action of centrifugal force on theknives will not tend to displace them. It is also desirable that anyadjustments of the knives in the head should be made without disturbingthe balance of the head on its rotational axis, for it has been foundthat any unbalancing of the head will, due to the high speed ofrotation, result in vibration and uneven operation.

According to the present invention I provide an improved cutter head soconstructed that the knives will be firmly held in position on the headwithout possibility of accidentaldisplacement, further provision beingmade for maintaining the balance of the head when the cutting knives areremoved and reassembled on the head for any reason. My improved headalso carries a maximum number of knives and the above and otheradvantageous features of the invention will hereinafter more fullyappear, reference beinp; had to the accompanying; drawings, in whichFig. 1 is a view in end elevation of a cutter head embodying myinvention.

Fig. 2 is side elevation of the in Fig. 1.

E3 is a view of a portion of the head shown in Fig. 1, a portion of thisfigure being shown in section to more clearly show the details of theknife holding ncans.

b ur. 4t is a view showing; the various elements of one of thecompensating devices for clanuiinp; the knives in position on the head.

lt? ferrinp; first to Fig: 1 the device consists of a cylindrical metalblock 1 having a central opening 2 whereby the block 1 may bel'nountparts shown ed on a suitable arbor or mandrel not shown,

The block 1 is provided with a number of radial slots 3, the sides ofwhich are parallel at the bottom portions and are of substantially thesame width as a number of tools or knives 1 received in the slots 3. Theslots 3 are wider than the knives 4 at the periphery 17, 1927. SerialNo. 220,175.

of the block 1 and each slot further provides a bevelled portion 5underlying a lip 6 which extends parallel to the tool 4t and is spacedtherefrom.

, Each slot 3 also receives awedging block or gib 7 of substantially thesame length as a tool 4;, the gib 7 providing one face 8 in contact withthe tool 1 and another face 9 extend ing at right angles to the face 8.This face 9 is in engagement with the under side of the lip 6 and hascontiguous thereto a bevelled face 10, the inclination of whichcorresponds with the inclination of the bevelled portion of the slot at5. Thus each gib 7 is adapted to fit rather closely in a slot 3 and iscapable of movement therein only in the direction of the tool 4, the lip6 preventing radial movement of the gib 7 with respect to the rotationalaxis of the cutter head.

Each slot 3 has communicating therewith two or more radially boredrecesses 11 which enter into the bevelled portion 5 of each slot andextend below the same. Each recess 11 receives a nut 12 having sidefaces 13 with the same inclination as the face of the gib 7 The nut 12provides a threaded opening 1% which receives an externally threadedsleeve 15 provided with tool receiving slots 16 at one end whereby thesleeve 15 may be turned in the nut 12. The sleeve 15 provides a centralthreaded opening 17 threaded oppositely with respect to the opening 14to receive a threaded stud 18 which extends throrurh the sleeve 15 andis provided at its end with a squared portion. 19 which is received in acorrespondingly shaped opening 20 of a plate The plate 21 fits closelyin the bottom of the recess 11 and so prevents the stud 18 from turning.

It will be noted that the threaded sleeve 15 is in contact at its lowerend with the plate 21 so that with the parts in. position as shown inFig. 3,1110 sleeve 15 cannot move an y deeper into the recess 11.Consequently when the sleeve 15 is turned in a clock-wise direction itwill cause the nut 12 to tend to move radially outward from the axis ofthe block 1. As this occurs the inclined face 13 of the nut 12 which isin engagement with the bevel face 10 of the gib 7 causes the gib 7 toexert a side pressure tending to hold the knife 1 in its slot 3. Aspreviously pointed out the gib 7 cannot move in radial direct-ionbecause of its engagement with the lip 6, so that the entire forceexerted by the nut 12 resolves itself into a pressure tending to holdknife 4 in its slot.

As previously pointed out the sleeve 15 is also internally threaded toreceive the stud 18 and as the threads on stud 18 are opposite to thethreads in nut 12, turning of the sleeve 15 Will result in moving thestud 18 in a direction opposite to the movement of the nut 12. Therelative pitch between the threads 15" on sleeve 15 and the threads 18on stud 18 isdetermined by the relation between the weights of the-nut12 and of the stud 18 respectively. In other Words, thethreads 15 and1-8 hear such a relation that when the nut 12 and the stud 18 are movedin opposite direct-ions by turning the sleeve 15 the position of thecenter of gravity of the parts so moved remains unchanged. Another wayof stating the same proposition is that any loosening and tightening ofthe tool clamping device, as described above," will not affect thebalance of thewhole tool head and the manner in which this works out inpractice will now be discussed.

When the cutter head embodying my invention is first assembled atthefactory, all of the cutter blades or knives t are of substantially thesame weight and proportion, although there may. be a very slightvariation in the thicknesses of the knives 4. The various parts enteringinto each clamping device including the nut 12, sleeve 15 and the stud18 are also made identical, so that when all of the knives 4 areassembled in slots 3 and clamped therein the entire cutter head is inperfect balance and can be driven at a high speed of rotation withoutvibration.

After a cutter head has been used in service for some time'the knivesetbecome dull and it is necessary to remove them from the cutter head inorder that the knives may be reground. This regrinding is very carefullydone so that each knife has the same amount of metal removed therefrom,but even with this precaution, there is no assurance that eachknif'e'will be returned to the same slot in which it was originallyassembled. Conseqnently when the reground knives A are again'clampedinthe head, any slight variations in the thickness of the knives willnecessitate changing the original adjustments of the clamping devices.However, each one of my improved clamping devices automaticallycompensates for any readjustments of its parts,'for any inward oroutward movement of the nut 12 from its original setting will becounterbalancedby the oppositeoutward or inward movement of the stud 18of such 'an amount to maintain the center of gravity of each clampingdevice substantially unchanged. Consequently when all of the knives 4;have been reset, the cutter head will rotate withits balance unaltereddue to the fact that the radius of gyration of each clamping device isthe same as for the original adjustment of the device.

It is also apparent that minor :uljustmcnls of the cutter head to insurethat the knives are tightly clamped has no effect on the balance of thehead. The balance remains uir changed, even though the operator makingthe adjustment applies different degrees of force to turn the varioussleeves 15 to clamp the knives. This is a feature wherein my improvedcutter head differs from those previously constructed with no provisionfor compensation of the amount of :uljustment in each clamping device.

It will be noted in Fig. 1 that the extend completely across the block 1and completely till the spaces between the wives 1 and the oppositeedges of the slots 3. Corn sequently there is no tendency for pitch fromthe wood being cut accumulating in the slots and making it dillicult toremove the knives 1 when this pitch hard'cns. Nor is there anypossibility of the pitch getting between the co-acting wedging faces ofthe gibs 7 and the nuts 12. My improved construction makes it possibleto place a maximum number of knives on a cutter head of given diameterowing to the fact that the slots 3 are only wide enough to receive theknives and gibs 7. The boring of the recesses 11 for receiving theclamping devices does not weaken the metal between adjacent slots to anygreat extent so that the slots 3 can be placed almost as closelytogether as clca 'ances between adjacent slots and recesses will permit.

I claim:

1. An improved cutter head comprising a rotatable body providin; slotsextending in a generally radial direction from the axis of said body,knives received in said slots and clamping devices for said knivesprovidmg means for securing varying degrees of pressure on said knivesagainst the sides of the slots and means for compensating for changes inposition of said pressure cxcrl ing means to maintain the rotatable bodyalways in balance.

2. An improved cutter head comprising a rotatable body providing radialslot s, knives received in said slots and a retaining device for eachknife comprising a clamping mcmbcr movable only at right angles to itskni to and members radially movable in oppmito directions for impartingmovement to said clani'ping member withoutaltcring the position of thecenter of gravity of said retaining device, as a whole.

3. An in'iproved cutter head comprising a rotatable body providingradial slots, knives received in said slots and a retaining device foreach of said knives con'iprising a clamping member movable only at rightangles to its knife, a wedging member movable parallel to said knife tooperate said clamping member and a compensating member movable in adirection opposite to that of said wedging member whereby the center ofgravity lllll a Wedging member in a recess, a stud passing through5211C]. Wedging member and a threaded member adapted to move saidwedglng member and said stud in opposite directions whereby to maintainunchanged the position of the center of gravity of said retaining deviceWhen the Wedging member is moved to cause said clamping; member to exerta sidewise pressure on said knife.

CHARLES WOLF.

